Not Applicable.
Not Applicable.
The invention relates to a tool for inserting prostheses within the body, and more particularly to tools for inserting prostheses, such as artificial disks, within an intervertebral space.
Spinal surgery involves many challenges as the long-term health and mobility of the patient often depends on the surgeon""s technique and precision. One type of spinal surgery involves the removal of the natural disk tissue that is located between adjacent vertebral bodies. Procedures are known in which the natural, damaged disk tissue is replaced with an interbody cage or fusion device, or with a disk prosthesis.
The insertion of an article, such as an artificial disk prosthesis, presents the surgeon with several challenges. The adjacent vertebral bodies collapse upon each other once the natural disk tissue is removed. These bodies must be separated to an extent sufficient to enable the placement of the prosthesis. However, if the vertebral bodies are separated, or distracted, to beyond a certain degree, further injury can occur. The disk prosthesis must also be properly positioned between the adjacent vertebral bodies. Over-insertion, or under-insertion of the prosthesis can lead to pain, postural problems and/or limited mobility or freedom of movement.
Specialized tools have been developed to facilitate the placement of devices, such as disk prosthesis, between adjacent vertebral bodies of a patient""s spine. Among the known tools for performing such procedures are separate spinal distractors and insertion devices. The use of separate tools to distract the vertebral bodies and insert a disk prosthesis or graft can prove cumbersome. Further, the use of some distractors can cause over-distraction of the vertebral bodies.
Exemplary devices for installing prosthesis and/or grafts between vertebral bodies are disclosed in U.S. Pat. Nos. 5,431,658 and 5,505,732. U.S. Pat. No. 5,431,658 discloses a facilitator device for the insertion of bone grafts between two adjacent vertebrae. The disclosed tool has two flat, tong-like guides that distract the vertebrae as a screw-type inserter forces the graft between the distracted vertebrae. U.S. Pat. No. 5,505,732 discloses an apparatus and a method of inserting spinal implants. The intervertebral space is first distracted and a hollow sleeve having teeth at one end is then driven into the vertebrae that are adjacent the disk space. A drill is then passed through the hollow sleeve, removing the disk and the bone in preparation for receiving the spinal implant, which is then inserted through the sleeve.
Despite existing tools and technologies, there remains a need to provide a device to facilitate the proper and convenient insertion of an object, such as a disk prosthesis, between adjacent vertebral bodies while minimizing the risk of further injury to the patient.
The present invention provides a device useful for implanting prostheses, such as artificial spinal disks, within a patient in a safe and efficient manner. The installation tool of the invention comprises a pair of opposed levers, each of which has a proximal handle portion and a distal portion. A fulcrum is disposed between the two levers to enable proper operation of the tool. The tool further comprises a pusher block that is positioned between the two levers. The pusher block is selectively movable between an initial location distal of the fulcrum and a final location adjacent the distal end of the levers. A pusher rod, which facilitates movement of a pusher block, has a distal end connected to the pusher block and a proximal, handle end.
Each lever is substantially elongate and the distal portion of each lever comprises an outwardly facing surface that terminates distally in a stop surface and an inwardly facing surface that extends distally beyond the stop surface. Preferably, the outwardly facing surface of each lever is substantially smooth. In one embodiment the stop surface of each lever defines a distal facing wall that is adapted to abut a vertebral body to facilitate proper installation of an artificial disk.
Each lever has opposed side walls and each side wall has a track defined therein. The cross section of each lever may be in the form of an I-shape or a T-shape, and each track in the lever side walls has opposed rails that are separated by a centrally disposed groove. The pusher block may be configured with upper and lower recesses formed in the upper and lower surfaces thereof, wherein each recess is adapted to seat one of the levers. In this embodiment each of the upper and lower recesses has opposed, substantially vertical walls that are separated by a substantially horizontal base wall. Each of the vertical side walls that define the recess of the pusher block preferably has, on an inner surface thereof, a protruding guide post that is adapted to mount within one of the tracks of the levers.
In one embodiment the handle portion of the levers may include protrusions that facilitate blade extraction using a tool such as a slap hammer or a slap fork. In another embodiment, the distal portion of the levers may be configured to permit adjustment of blade tip length.
The installation tool of the invention can be used in the following manner. Once the natural, damaged disk tissue is removed from a patient and the area is prepared to receive an artificial disk, the artificial disk is loaded between the levers of the installation tool so that a posterior side of the disk abuts a distal end of the pusher block. The distal tip of the levers is then positioned between the vertebral bodies such that the outwardly facing surfaces of each lever contacts opposed vertebral bodies. Once this position is achieved, the pusher rod is advanced distally, causing the pusher block and the artificial disk to likewise move distally along the inner surfaces of the levers. As the artificial disk and the pusher rod move distally, or forward, the levers separate and also cause vertical separation of the adjacent vertebral bodies. In the proper position the distal facing surfaces of the two levers should contact the vertebral bodies. Once such contact is achieved between the distal facing surfaces of the levers and the vertebral bodies, and the artificial disk begins to be positioned between the two vertebral bodies, further forward movement of the pusher block, causes the blade tips of the levers to retract from between the vertebral bodies and to eject the artificial disk. This tool thus enables the proper positioning of the artificial disk between the vertebral bodies, without over-insertion or under-insertion of the artificial disk, while minimizing the degree of distraction of the vertebrae.